1. Field of the Invention
The present invention relates to an ice making machine wherein a number of ice cubes are simultaneously formed in a multiplicity of individual open-bottom freezing cells and thereupon automatically released from the freezing cells for discharge into an ice storage bin, and more particularly to an electric control apparatus for the ice making machine to insure complete freezing of all the water in the freezing cells in operation under the power supply of different frequency.
2. Description of the Prior Art
In such ice making machines as described above, the water circulated into the freezing cells from a water reservoir is formed into ice cubes during the freezing cycle, and the formed ice cubes are discharged into an ice storage bin during the harvesting cycle. It is, therefore, essential to accurately initiate and terminate the freezing cycle to insure the formation of the desired ice cubes. To this end, various control devices have been proposed for the ice making machines.
For example, Japanese Patent Early Publication No. 61-180868 discloses a control device which is arranged to control the freezing cycle in accordance with changes of an ambient temperature of the machine for producing the desired ice cubes of uniform thickness. However, the compressor of the ice making machine is driven by an alternating voltage applied thereto from a commercially available power source. For this reason, the rotation speed of the compressor under the power supply of 60 Hz will differ from that of the compressor under the power supply of 50 Hz. This causes a difference in ice making capacity of the machine. In the case that the freezing cycle in operation under the power supply of 60 Hz is maintained for a predetermined period sufficient to insure complete freezing of all the water in the freezing cells, a part of the water in the freezing cells may not be frozen into ice cubes for the predetermined period in operation under the power supply of 50 Hz. In the case that the freezing cycle in operation under the power supply of 50 Hz is maintained for a predetermined period sufficient to insure complete freezing of all the water in the freezing cells, the water in the freezing cells is excessively frozen in operation under the power supply of 60 Hz.